Numerical Simulation And Experimental Study On Composite Surface Strengthening Of TC4 Titanium Alloy By Secondary Shot Peening And Ultrasonic Rolling

Facing the demand of high-end aerospace equipment manufacturing technology,based on the crack initiation mechanism of TC4 titanium alloy in service,the surface of TC4 titanium alloy was modified by the secondary shot peening-ultrasonic rolling surface composite strengthening process,and the effects of single strengthening and composite strengthening process on the surface properties of TC4 titanium alloy such as residual stress,surface texture,microhardness and surface morphology were explored.Firstly,the orthogonal experimental design is used to arrange the measured parameters horizontally,and the mathematical methods such as mean,range and variance are used to calculate and analyze them.The analysis results show that the measurement parameters with 9 ψ angles,3mm collimator diameter and 5s exposure time have small numerical error,good stability and high measurement efficiency.Secondly,according to the spherical Hertzian contact theory and the movement characteristics of surface strengthening,the finite element models of random shot peening,ultrasonic rolling and secondary shot peening-ultrasonic rolling surface strengthening are constructed,and the influence of processing parameters in shot peening and ultrasonic rolling strengthening processes on the surface modification effect of TC4 titanium alloy is clarified through orthogonal experimental design.The calculation results show that the maximum residual compressive stress is 1273.71 MPa and the thickness of residual compressive stress layer reaches 0.24mm;when the diameter of large shot is 0.6mm,the diameter of small shot is 0.4mm,the shot peening speed is 70m/s and the coverage rate is 200%.Under the conditions of static pressure of1100 N,amplitude of 10μm,feed speed of 2m/min and rolling times of 4 times,the maximum residual compressive stress is 920.78 MPa,and the depth of residual compressive stress field reaches 0.5mm;The maximum residual compressive stress is1365.43 MPa and the depth of residual compressive stress field reaches 0.6mm under the combined strengthening of secondary shot peening and ultrasonic rolling.Finally,the surface texture,microhardness and surface morphology of TC4 titanium alloy samples under different surface strengthening were tested.The experimental analysis results show that the surface modification effect under the combined surface strengthening of secondary shot peening and ultrasonic rolling is better,and the surface microhardness is424.75 HV and the surface roughness Ra is 0.826μm.